Allah's Messenger (ﷺ) said, "(A believer) who accompanies the funeral
procession of a Muslim out of sincere faith and hoping to attain
Allah's reward and remains with it till the funeral prayer is offered
and the burial ceremonies are over, he will return with a reward of
two Qirats. Each Qirat is like the size of the (Mount) Uhud. He who
offers the funeral prayer only and returns before the burial, will
return with the reward of one Qirat only."
Sahih al-Bukhari Book 2, Hadith 40